The lower jaw is made of just one bone, known as the mandible. Jaw closure is the result of contraction of a group of muscles which do not contract singly. They all perform their functions synergistically. The smooth and coordinated function of these muscles is essential for the proper occlusion of the teeth. The mandibular elevators, which close the lower jaw, include the coordinated function of the masseter, temporal, and medial pterygoid muscles. The mandibular depressors which open the lower jaw include the activity of the external pterygoid and the suprahyoid muscles. Protrusion of the mandible is performed by the masseter, internal pterygoid, and the external pterygoid muscles. Retrusion of the mandible is accomplished by the temporal and digastic muscles
Mandibular jaw closure depends on functional integrity of a group of muscles which perform their functions simultaneously. The smooth function of these muscles is essential for the proper occlusion of the teeth.
When these muscles and surrounding tissues are impaired due to injury or surgery, disclusion or malocclusion of the teeth often takes place.
When a tensile strain history is imposed on tissue, its physical properties will be changed and/or enhanced dependent on the applied strain and its direction. Tissue will change or remodel its volume, length and mass from a reference structure to a new structure, given a specific strain history imposed on that tissue. Thus, strain can be directed and manipulated so as to accomplish desired and beneficial tissue changes.
Repetitive and rhythmic opening and closing of the mandible, if properly administered, can induce strains within the oral tissue and surrounding structures, which result in enhanced healing and rapid pain reduction or suppression, thereby facilitating and accelerating the complete healing and rehabilitation of the tissue structures of the oral cavity to the point that healed structure can properly and adequately perform its specific function, and can contribute to the overall function of the oral cavity as well as of the total temporomandibular joint.
Rehabilitation of the structures of the oral cavity and of the TMJ (the actual muscle training and tissue healing) can be viewed as being voluntary, semi-voluntary and involuntary.
In U.S. Pat. No. 4,700,695 is described a semi-voluntary, cam-operated jaw-opening system including an intraoral cam arrangement for periodically opening (but not closing) the lower jaw. This arrangement relies upon the user's mandibular elevator muscles to return the jaw. But, frequently and for well-known reasons, a patient's elevator muscles may be under anesthetic agents, or they may be suffering from a disease, or they may have become detached during surgery
As such, they may be under too much pain and swelling and incapable of closing the jaw. Normally it may take at least a few weeks before these muscles will reattach to the mandible and start properly functioning again.
This patented semi-voluntary cam arrangement requires two intraoral cams, two maxillary tooth-engaging plates, two mandibular tooth-engaging plates, cam riding grooves within the mandibular plates, and a pair of motor driven cables for reciprocating both cams intraorally.
These intraoral cams require critical positioning and aligning within their assigned grooves, and the slack in the cables may also have to be adjusted.
Some patients may require an attendant to make such adjustments so that all these parts will perform their functions simultaneously and in synchronism as intended in order to achieve proper bilateral jaw opening.
It is an object of this invention to provide an involuntary extraoral cam-operated jaw oscillator system, which can be quickly and easily attached to the maxillary and mandibular arches.